JP6432548B2 - Engine control device - Google Patents

Description

  The present invention relates to an engine control device, and more particularly, to an engine control device that controls an engine to output a target torque.

  In general, when the operating region of a spark ignition engine is, for example, a relatively low rotation and high load region, the unburned mixture (end gas) self-ignites before the flame spreading around the spark plug propagates. It is known that so-called knocking that generates a shock wave is likely to occur. Particularly in recent years, for the purpose of improving the performance of the engine, the compression ratio is increased and the intake air is supercharged by a supercharger, and knocking is more likely to occur.

  Since knocking can cause an increase in noise and engine damage, the ignition timing is retarded (ignition retard) as necessary to suppress knocking. Specifically, when knocking is detected by a knock sensor attached to the engine, the peak of the combustion pressure is lowered by retarding the ignition timing to suppress knocking. When knocking is not detected, the ignition timing is gradually advanced (for example, see Patent Document 1).

JP 2008-64032 A

In a state where knocking has not occurred, the ignition timing is normally set in the vicinity of MBT (Minimum Advance for Best Torque) that generates the maximum torque. Therefore, when knocking is detected and ignition retard is performed, the output torque decreases accordingly.
Therefore, when ignition retard is performed, it is conceivable to increase the intake air amount so as to offset the torque decrease due to this ignition retard and maintain the output torque.

  However, if the intake air amount is excessively increased, the thermal efficiency of the engine decreases, so that the output torque cannot be maintained despite the increase of the intake air amount, resulting in deterioration of fuel consumption.

  The present invention has been made to solve the above-described problems of the prior art, and is capable of suppressing a decrease in torque associated with ignition retard for preventing knocking and preventing deterioration of fuel consumption. An object is to provide a control device.

In order to achieve the above object, an engine control apparatus according to the present invention is an engine control apparatus that controls an engine so as to output a target torque. The ignition timing setting means that is set according to the state, the ignition timing correction means that corrects the reference ignition timing to the retard side to suppress knocking, and the target air amount for causing the engine to output the target torque Target air amount setting that is set using the reference thermal efficiency according to the engine operating condition under the condition that the timing is set to the reference ignition timing, or the actual thermal efficiency estimated based on the intake air amount, the engine speed, and the ignition retard amount means and the target air amount, the target air-to reference thermal efficiency in accordance with the operating condition of the engine is limited so as not to exceed the threshold set to be equal to or greater than the predetermined value And an air amount control unit that controls the intake air amount in accordance with the target air amount that is limited to the threshold value or less by the target air amount limiting unit, and the threshold value is a region where the engine load is relatively low. In an area where the engine load is relatively constant regardless of the engine speed at the same engine load, and the engine load is relatively high, the engine speed is relatively high and the engine speed is relatively high. It is characterized by being set to be higher in the region between the high rotation region and the low rotation region than in the low low rotation region.
In the present invention configured as described above, the target air amount restriction means restricts the target air amount set according to the ignition timing so as not to exceed the threshold value set according to the operating state of the engine. If the intake air amount is excessively increased beyond the threshold, the thermal efficiency is reduced, and the target torque cannot be obtained despite the increase in the target air amount. It is possible to prevent a deterioration in the vicious circle, thereby suppressing a decrease in torque associated with ignition retard for preventing knocking and preventing deterioration in fuel consumption. Further, the target air amount restriction means restricts the target air amount so as not to exceed the threshold value set so that the thermal efficiency becomes a predetermined value or more, so that the intake air amount is excessively increased beyond the threshold value. Even if the target air amount is increased, the target torque cannot be obtained, and it is possible to prevent the thermal efficiency from decreasing to a region where the target air amount further increases and the fuel consumption deteriorates, thereby preventing knocking. As a result, it is possible to suppress a decrease in torque associated with the ignition retard and to reliably prevent deterioration of fuel consumption.

In the present invention, it is preferable that the target air amount limiting means limits the target air amount so as not to exceed a threshold set so as to increase as the engine load increases at the same engine speed.
In the present invention configured as described above, the target air amount limiting means can limit the target air amount so as to be equal to or less than a threshold value appropriately set according to the engine speed and the engine load. As a result, it is possible to suppress a decrease in torque associated with ignition retard for preventing knocking and to reliably prevent deterioration of fuel consumption.

In the present invention, it is preferable that the target air amount limiting means does not exceed a threshold value set so that the target air amount is constant in a region where the engine load is relatively high at the same engine speed. Restrict.
In the present invention configured as described above, the target air amount restriction means can restrict the target air amount so as to be equal to or less than a threshold value appropriately set according to the engine load, thereby preventing knocking. As a result, it is possible to suppress a reduction in torque associated with the ignition retard for and to reliably prevent deterioration of fuel consumption.

In the present invention, preferably, the target air amount setting means sets the target air amount based on the lower reference thermal efficiency or actual thermal efficiency of the reference thermal efficiency and the actual thermal efficiency.
In the present invention configured as described above, the target air amount setting means sets the target air amount based on the lower thermal efficiency of the reference thermal efficiency and the actual thermal efficiency, so that a reduction in thermal efficiency due to ignition retard is taken into account. Thus, it is possible to set the target air amount, and thus it is possible to surely suppress the torque decrease accompanying the ignition retard for preventing knocking and to prevent the deterioration of fuel consumption.

  According to the engine control apparatus of the present invention, it is possible to suppress a decrease in torque associated with ignition retard for preventing knocking and to prevent deterioration of fuel consumption.

1 is a schematic configuration diagram of an engine system to which an engine control device according to an embodiment of the present invention is applied. It is a block diagram which shows the electric constitution of the control apparatus of the engine by embodiment of this invention. It is a flowchart of the engine control process which the engine control apparatus by embodiment of this invention controls an engine. It is a flowchart of the target charging efficiency setting process in which the control apparatus of the engine by embodiment of this invention sets target charging efficiency. FIG. 5 is a control block diagram illustrating a method by which a PCM according to an embodiment of the present invention calculates a required filling efficiency. It is a map which shows the restriction | limiting filling efficiency set according to the engine speed and the request | requirement average effective pressure. FIG. 7A is a time chart showing a time change of a parameter related to engine control when an accelerator operation is performed in a vehicle equipped with an engine control device according to an embodiment of the present invention. FIG. FIG. 7B is a chart showing a change in the target torque when the accelerator opening changes as shown in FIG. 7A, and FIG. 7C is set to suppress knocking. FIG. 7D is a chart showing changes in the ignition retard amount, FIG. 7D is a chart showing changes in charging efficiency set to output the target torque of FIG. 7B to the engine, and FIG. 7E is FIG. FIG. 7F is a chart showing a change in the throttle opening controlled so as to realize the charging efficiency of d), and FIG. 7F is an advance amount of the intake VVT controlled so as to realize the charging efficiency of FIG. of Chart showing the reduction, shown in FIG. 7 (g) is FIG. 7 (e), the is a chart showing changes in engine speed controlled engines as (f).

  Hereinafter, an engine control apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.

  First, an engine system to which an engine control apparatus according to an embodiment of the present invention is applied will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic configuration diagram of an engine system to which an engine control device according to an embodiment of the present invention is applied. FIG. 2 is a block diagram showing an electrical configuration of the engine control device according to the embodiment of the present invention. is there.

  As shown in FIGS. 1 and 2, the engine system 100 mainly includes an intake passage 1 through which intake air (air) introduced from the outside passes, intake air supplied from the intake passage 1, and fuel injection to be described later. An engine 10 (specifically, a gasoline engine) that generates fuel for the vehicle by burning an air-fuel mixture supplied from the valve 13 and an exhaust passage 25 that discharges exhaust gas generated by combustion in the engine 10. And sensors 40 to 54 for detecting various states relating to the engine system 100, and a PCM 60 (engine control device) for controlling the entire engine system 100.

  In the intake passage 1, in order from the upstream side, the air cleaner 3 that purifies the intake air introduced from the outside, the compressor 4 a of the turbocharger 4 that boosts the intake air that passes through, and the outside air or cooling water cools the intake air. An intercooler 5, a throttle valve 6 that adjusts the amount of intake air (intake air amount) that passes through, and a surge tank 7 that temporarily stores intake air supplied to the engine 10 are provided.

  The intake passage 1 is provided with an air bypass passage 8 for returning a part of the intake air supercharged by the compressor 4a to the upstream side of the compressor 4a. Specifically, one end of the air bypass passage 8 is connected to the intake passage 1 downstream of the compressor 4a and upstream of the throttle valve 6, and the other end of the air bypass passage 8 is downstream of the air cleaner 3 and The intake passage 1 is connected to the upstream side of the compressor 4a.

  The air bypass passage 8 is provided with an air bypass valve 9 that adjusts the flow rate of intake air flowing through the air bypass passage 8 by an opening / closing operation. The air bypass valve 9 is a so-called on / off valve that can be switched between a closed state in which the air bypass passage 8 is completely closed and an open state in which the air bypass passage 8 is completely opened.

  The engine 10 mainly supplies an intake valve 12 for introducing the intake air supplied from the intake passage 1 into the combustion chamber 11, a fuel injection valve 13 for injecting fuel toward the combustion chamber 11, and a supply to the combustion chamber 11. Spark plug 14 for igniting the mixture of the intake air and fuel, a piston 15 reciprocating by combustion of the air-fuel mixture in the combustion chamber 11, a crankshaft 16 rotated by reciprocating motion of the piston 15, and combustion And an exhaust valve 17 that exhausts exhaust gas generated by combustion of the air-fuel mixture in the chamber 11 to the exhaust passage 25.

  In addition, the engine 10 has variable intake valve mechanisms 18 and variable exhaust valve mechanisms in which the operation timings (corresponding to valve phases) of the intake valve 12 and the exhaust valve 17 are variable valve timing mechanisms. 19 is variably configured. As the variable intake valve mechanism 18 and the variable exhaust valve mechanism 19, various known types can be applied. For example, the operation of the intake valve 12 and the exhaust valve 17 is performed using a mechanism configured in an electromagnetic or hydraulic manner. Timing can be changed.

  The exhaust passage 25 is rotated by exhaust gas passing through in order from the upstream side, and the turbine 4b of the turbocharger 4 that drives the compressor 4a by this rotation, such as a NOx catalyst, a three-way catalyst, an oxidation catalyst, etc. Exhaust gas purification catalysts 26a and 26b having an exhaust gas purification function are provided. Hereinafter, when the exhaust purification catalysts 26a and 26b are used without being distinguished from each other, they are simply referred to as “exhaust purification catalyst 26”.

  The exhaust passage 25 is connected to an exhaust gas recirculation (hereinafter referred to as “EGR”) passage 27 for returning a part of the exhaust gas to the intake passage 1. One end of the EGR passage 27 is connected to the exhaust passage 25 on the upstream side of the turbine 4 b, and the other end is connected to the intake passage 1 on the downstream side of the throttle valve 11. Further, the EGR passage 27 is provided with an EGR cooler 28 that cools the exhaust gas to be recirculated and an EGR valve 29 that controls the flow rate of the exhaust gas flowing through the EGR passage 27.

  Further, the exhaust passage 25 is provided with a turbine bypass passage 30 for bypassing the turbine 4b of the turbocharger 4 for exhaust. The turbine bypass passage 30 is provided with a waste gate valve (hereinafter referred to as “WG valve”) 31 for controlling the flow rate of the exhaust gas flowing through the turbine bypass passage 30.

The engine system 100 is provided with sensors 40 to 54 that detect various states relating to the engine system 100. Specifically, these sensors 40 to 54 are as follows. The accelerator opening sensor 40 detects an accelerator opening that is an accelerator pedal opening (corresponding to an amount by which the driver has depressed the accelerator pedal). The air flow sensor 41 detects an intake air amount corresponding to the flow rate of the intake air passing through the intake passage 1 between the air cleaner 3 and the compressor 4a. The first temperature sensor 42 detects the temperature of the intake air passing through the intake passage 1 between the air cleaner 3 and the compressor 4a. The first pressure sensor 43 detects the supercharging pressure. The throttle opening sensor 44 detects the throttle opening that is the opening of the throttle valve 6. The second pressure sensor 45 detects intake manifold pressure (pressure in the surge tank 7) corresponding to the pressure of intake air supplied to the engine 10. The crank angle sensor 46 detects the crank angle in the crankshaft 16. The intake side cam angle sensor 47 detects the cam angle of the intake camshaft. The exhaust side cam angle sensor 48 detects the cam angle of the exhaust camshaft. The EGR opening degree sensor 49 detects the opening degree of the EGR valve 29. The WG opening degree sensor 50 detects the opening degree of the WG valve 31. The O ₂ sensor 51 detects the oxygen concentration in the exhaust gas. The exhaust temperature sensor 52 detects the exhaust temperature. The vehicle speed sensor 53 detects the speed of the vehicle (vehicle speed). The knock sensor 54 is provided, for example, in a cylinder block of the engine 10 and detects vibration caused by knocking of the engine 10. These various sensors 40 to 54 output detection signals S140 to S154 corresponding to the detected parameters to the PCM 60, respectively.

  The PCM 60 controls the components in the engine system 100 based on the detection signals S140 to S154 input from the various sensors 40 to 54 described above. Specifically, as shown in FIG. 2, the PCM 60 supplies a control signal S106 to the throttle valve 6, controls the opening / closing timing and throttle opening of the throttle valve 6, and sends a control signal S109 to the air bypass valve 9. To supply the control signal S131 to the WG valve 31, to control the opening of the WG valve 31, to supply the control signal S113 to the fuel injection valve 13, The injection amount and the fuel injection timing are controlled, the control signal S114 is supplied to the spark plug 14, the ignition timing is controlled, and the control signals S118 and S119 are supplied to the variable intake valve mechanism 18 and the variable exhaust valve mechanism 19, respectively. Thus, the operation timing of the intake valve 12 and the exhaust valve 17 is controlled.

For example, the PCM 60 sets the reference ignition timing by the spark plug 14 according to the operating state of the engine 10 and corrects the reference ignition timing to the retard side in order to suppress knocking. Further, the PCM 60 sets the target charging efficiency (a value obtained by making the intake air amount non-dimensional) for outputting the target torque to the engine 10 in accordance with the ignition timing and in accordance with the ten operating states. The charging efficiency is controlled by limiting the throttle valve 6, the WG valve 31, the intake valve 12, the exhaust valve 17, and the like according to the target charging efficiency.
The PCM 60 stores a CPU, various programs that are interpreted and executed on the CPU (including basic control programs such as an OS and application programs that are activated on the OS to realize specific functions), and programs and various data. And a computer having an internal memory such as a ROM and a RAM.
The PCM 60 corresponds to the “engine control device” in the present invention, and “ignition timing setting means”, “ignition timing correction means”, “target air amount setting means”, and “target air amount restriction means” in the present invention. , And “air amount control means”.

Next, an engine control process performed by the engine control device will be described with reference to FIGS.
FIG. 3 is a flowchart of an engine control process in which the engine control apparatus according to the embodiment of the present invention controls the engine, and FIG. 4 is a target filling in which the engine control apparatus according to the embodiment of the present invention sets the target charging efficiency. FIG. 5 is a control block diagram showing how the PCM according to the embodiment of the present invention calculates the required charging efficiency, and FIG. 6 shows the efficiency setting process according to the engine speed and the required average effective pressure. FIG. 6 is a map showing the limited filling efficiency set in FIG.

The engine control process of FIG. 3 is started and executed repeatedly when the ignition of the vehicle is turned on and the engine control device is turned on.
When the engine control process is started, as shown in FIG. 3, in step S1, the PCM 60 acquires the driving state of the vehicle. Specifically, the PCM 60 includes an accelerator opening detected by the accelerator opening sensor 40, an intake air amount detected by the airflow sensor 41, a vehicle speed detected by the vehicle speed sensor 53, presence / absence of knocking detected by the knock sensor 54, vehicle The detection signals S140 to S154 output from the above-described various sensors 40 to 54, including the gear stage currently set for the transmission of, are acquired as the operating state.

  Next, in step S2, the PCM 60 sets a target acceleration based on the driving state of the vehicle including the operation of the accelerator pedal acquired in step S1. Specifically, the PCM 60 determines the acceleration corresponding to the current vehicle speed and gear stage from acceleration characteristic maps (created in advance and stored in a memory or the like) defined for various vehicle speeds and various gear stages. A characteristic map is selected, and a target acceleration corresponding to the current accelerator opening is determined with reference to the selected acceleration characteristic map.

  Next, in step S3, the PCM 60 determines a target torque of the engine 10 for realizing the target acceleration determined in step S2. In this case, the PCM 60 determines a target torque within a range of torque that can be output by the engine 10 based on the current vehicle speed, gear stage, road surface gradient, road surface μ, and the like.

In parallel with the processing in steps S2 to S3, in step S4, the PCM 60 determines whether knocking has been detected based on the detection signal acquired from the knock sensor 54 in step S1.
As a result, when knocking is detected, the process proceeds to step S5, and the PCM 60 increases the correction amount (ignition retard amount) when correcting the ignition timing to the retard side in order to suppress knocking. On the other hand, if knocking is not detected, the process proceeds to step S6, and the PCM 60 decreases the ignition retard amount. Thus, every time knocking is detected by the knock sensor 54, the ignition timing is gradually corrected to the retard side, and when knocking is not detected, the ignition timing is returned to the advance side. However, the ignition retard amount is set so as not to exceed the limit value (retard angle limit) of the retard amount determined in advance from an experiment from the viewpoint of combustion stability in consideration of significant deterioration in combustion efficiency and misfire.

  After step S3 and step S5 or S6, the process proceeds to step S7, where the PCM 60 performs ignition according to the operating state of the engine 10 including the current engine speed acquired in step S1 and the target torque determined in step S3. The reference ignition timing by the plug 14 is set. Specifically, the PCM 60 calculates a target indicated torque by adding a loss loss due to friction loss or pumping loss to the target torque, and defines the relationship between the ignition timing and the indicated torque for various charging efficiencies and various engine speeds. The ignition advance map that corresponds to the current engine speed and obtains the target indicated torque in the vicinity of the MBT is selected from the ignition advance maps (previously created and stored in a memory or the like). With reference to the ignition advance map, the ignition timing corresponding to the target indicated torque is set as the reference ignition timing. Then, the PCM 60 corrects the set reference ignition timing to the retard side by the ignition retard amount set in step S5 or S6.

  Next, in step S8, the PCM 60 executes a target charging efficiency setting process for setting a target charging efficiency for causing the engine 10 to output a target torque. This target filling efficiency setting process will be described with reference to FIGS.

  As shown in FIGS. 4 and 5, when the target filling efficiency setting process is started, in step S21, the pressure conversion unit 61 of the PCM 60 requires the required average to output the target indicated torque calculated in step S7. Calculate the effective pressure.

  Next, in step S22, the heat amount conversion unit 62 of the PCM 60 acquires a heat amount (required heat amount) corresponding to the required average effective pressure calculated in step S21. For example, the PCM 60 calculates the amount of work necessary to obtain the required average effective pressure by multiplying the required average effective pressure by the stroke volume, and acquires the amount of heat corresponding to this amount of work as the required heat amount.

  Next, in step S23, the reference thermal efficiency conversion unit 63 of the PCM 60 acquires the reference thermal efficiency based on the required average effective pressure and engine speed calculated in step S21. This reference thermal efficiency is the thermal efficiency when the ignition timing by the spark plug 14 is set to the reference ignition timing set in step S7. For example, the relationship between the average effective pressure and the thermal efficiency is defined for various engine speeds. A thermal efficiency corresponding to the required average effective pressure is obtained as a reference thermal efficiency by referring to a map corresponding to the current engine speed from a map (previously created and stored in a memory or the like).

  Next, in step S24, the actual heat efficiency conversion unit 64 of the PCM 60 estimates the actual heat efficiency based on the intake air amount and engine speed acquired in step S1 and the ignition retard amount set in step S5 or S6. To do. This actual thermal efficiency is the thermal efficiency according to the actual operating conditions of the engine 10, and is, for example, a map that defines the relationship between the ignition retard amount and the actual thermal efficiency for various intake air amounts and various engine speeds (prepared and stored in the memory). The thermal efficiency corresponding to the ignition retard amount is estimated as the actual thermal efficiency with reference to the map corresponding to the current intake air amount and the engine speed.

Next, in step S25, the PCM 60 compares the reference thermal efficiency with the actual thermal efficiency. As a result, when the actual heat efficiency is lower than the reference heat efficiency, the process proceeds to step S26, and the ce conversion unit 65 of the PCM 60 determines the target charging efficiency (hereinafter referred to as the charging efficiency as necessary) from the actual heat efficiency and the required heat amount. (referred to as efficiency)). Specifically, the PCM 60 calculates the amount of generated heat (efficiency reflected heat amount) necessary to obtain the required heat amount under the actual heat efficiency by dividing the required heat amount by the actual heat efficiency. The ce conversion unit 65 refers to a map (which is created in advance and stored in a memory or the like) that defines the relationship between the amount of generated heat and ce, and acquires ce corresponding to the efficiency reflected heat amount as a target ce.
On the other hand, when the actual thermal efficiency is equal to or higher than the reference thermal efficiency, the process proceeds to step S27, and the ce conversion unit 65 of the PCM 60 calculates the target ce from the reference thermal efficiency and the required heat amount. Specifically, the PCM 60 calculates the amount of generated heat (efficiency reflected heat amount) necessary to obtain the required heat amount under the reference heat efficiency by dividing the required heat amount by the reference heat efficiency. The ce conversion unit 65 refers to a map that defines the relationship between the amount of generated heat and ce, and acquires ce corresponding to the efficiency reflected heat amount as a target ce.

  After step S26 or S27, the process proceeds to step S28, and the PCM 60 refers to the ce restriction map 66 (prepared and stored in a memory or the like), and compares the target ce with the restriction ce.

  As a result, when the target ce is equal to or less than the limit ce, the process proceeds to step S29, and the PCM 60 sets the target ce as the request ce. On the other hand, if the target ce exceeds the limit ce, the process proceeds to step S30, and the PCM 60 sets the limit ce as the request ce. That is, the PCM 60 limits the request ce so as not to exceed the limit ce.

The limit ce is set according to the engine speed and the required average effective pressure. This limit ce is basically an upper limit value of ce at which the thermal efficiency becomes 30% or more at various engine speeds and required average effective pressures.
When the engine 10 is operated in an operation region where the required ce is not limited to the limit ce or less and the thermal efficiency is less than 30%, even if a slight ignition retard is performed, the output torque is greatly reduced. Therefore, the required ce is increased in order to achieve the target torque, and the fuel efficiency is deteriorated. Furthermore, as the ce increases, the engine 10 is operated in an operation region where the thermal efficiency is lower, so that the target torque cannot be obtained even though the required ce is increased, and the required ce further increases. This leads to a vicious cycle where fuel economy deteriorates. However, in the present embodiment, since the request ce is limited so as not to exceed the limit ce, the fuel consumption deterioration as described above can be prevented.

Specifically, as shown in the map of FIG. 6, the limit ce is set to increase as the required average effective pressure (that is, engine load) increases at the same engine speed. This corresponds to the fact that, when the engine speed is the same, the larger the required average effective pressure, the greater the ce required to realize the required average effective pressure. Further, the limit ce is set to be constant in a region where the required average effective pressure is relatively high, more specifically, in a region corresponding to a state where the accelerator opening is fully open.
In addition, since the operation area where the required average effective pressure is relatively low is an operation area where the thermal efficiency is low, the target torque cannot be obtained unless ce is increased, and the fuel consumption is low in the first place. Even if the thermal efficiency deteriorates to less than 30%, the effect on fuel consumption is small. Therefore, the limit ce in the operation region where the required average effective pressure is relatively low is set to a value corresponding to a thermal efficiency lower than 30% (for example, 22%).
The limit ce is set to be substantially constant regardless of the engine speed at the same required average effective pressure.

  Returning to FIG. 4, after step S29 or S30, the PCM 60 ends the target charging efficiency setting process and returns to the main routine.

  Returning to FIG. 3, after performing the target charging efficiency setting process of step S8, the process proceeds to step S9, where the PCM 60 introduces air corresponding to the request ce set in the target charging efficiency setting process into the engine 10. Considering the amount of air detected by the air flow sensor 31, the opening of the throttle valve 6 and the opening / closing timing of the intake valve 12 via the variable intake valve mechanism 18 are determined.

  Next, in step S10, the PCM 60 controls the throttle valve 6 and the variable intake valve mechanism 18 based on the throttle opening determined in step S9 and the opening / closing timing of the intake valve 12, and also according to the operating state of the engine 10 and the like. The fuel injection valve 13 is controlled based on the target equivalence ratio determined in this way and the actual air amount estimated based on the detection signal S141 of the airflow sensor 41 and the like.

  In parallel with the processing in steps S9 to S10, in step S11, the PCM 60 acquires the target supercharging pressure by the turbocharger 4. For example, a map indicating the relationship between the target torque and the target boost pressure is stored in advance in a memory or the like, and the PCM 60 acquires the target boost pressure corresponding to the target torque determined in step S3 with reference to the map. To do.

  Next, in step S12, the PCM 60 determines the opening degree of the WG valve 31 for realizing the target boost pressure acquired in step S11.

Next, in step S13, the PCM 60 controls the actuator of the WG valve 31 based on the opening set in step S12.
In this case, the PCM 10 controls the actuator of the WG valve 31 according to the opening set in step S12, and sets the supercharging pressure detected by the first pressure sensor 43 to the target supercharging pressure acquired in step S11. The actuator is feedback-controlled so that it approaches.

  In parallel with the processing in steps S9 to S10 and steps S11 to S13, in step S14, the PCM 60 controls the spark plug 14 so that ignition is performed at the ignition timing set in step S7.

If there is no request for torque reduction in step S22, the process proceeds to step S25, and the engine control unit 67 performs the actual introduction into the combustion chamber 11 under the control of the throttle valve 6 and the variable intake valve mechanism 18 in step S21. The spark plug 14 is controlled so that ignition is performed at the ignition timing (basic ignition timing) with the best combustion efficiency corresponding to the air amount.
Specifically, the engine control unit 67 sets the MBT of the ignition advance map corresponding to the actual air amount and the engine speed and the knock limit ignition timing corresponding to the actual air amount and the engine speed on the retard side. The ignition timing is set as the basic ignition timing, and the spark plug 14 is controlled.
After steps S10, S13, and S14, the PCM 60 ends the engine control process.

  Next, the operation of the engine control apparatus according to the embodiment of the present invention will be described with reference to FIG. FIG. 7 is a time chart showing changes over time in parameters relating to engine control when an accelerator operation is performed in a vehicle equipped with an engine control apparatus according to an embodiment of the present invention.

FIG. 7A is a chart showing changes in accelerator opening, and FIG. 7B is a chart showing changes in target torque when the accelerator opening changes as shown in FIG. 7A.
FIG. 7A shows a change in the accelerator opening when the accelerator pedal is operated so as to increase the vehicle speed at a substantially constant rate with the gear stage fixed. As shown in FIGS. 7A and 7B, the target torque changes basically in the same manner as the change in the accelerator opening.

FIG. 7C is a chart showing a change in the ignition retard amount set to suppress knocking, and FIG. 7D is a charging efficiency set to output the target torque of FIG. 7B to the engine. 7D, the solid line in FIG. 7D indicates the request ce limited so as not to exceed the limit ce, the broken line indicates the target ce before being limited to the limit ce, and the alternate long and short dash line Indicates the actual ce corresponding to the amount of air actually taken into the engine 10.
In the example of FIG. 7C, the ignition retard is performed at the timing when the target torque starts to increase in accordance with the increase in the accelerator opening. In order to compensate for the decrease in output torque due to the ignition retard, the target ce increases as shown by the broken line in FIG. However, as described with reference to FIGS. 4 and 5, the request ce is limited so as not to exceed the limit ce. That is, as shown by a solid line in FIG. 7D, when ignition retard is executed and the target torque is relatively high, the required ce is limited to a value lower than the target ce. Thereby, it is possible to prevent deterioration in fuel consumption due to excessively increasing ce and decreasing thermal efficiency. The actual ce is basically controlled so as to coincide with the required ce, as indicated by the alternate long and short dash line in FIG. 7D, but there is a slight delay when the required ce increases rapidly. . This is due to a delay in response of the intake air amount to the control of the throttle valve 6 and the variable intake valve mechanism 18.

FIG. 7 (e) is a chart showing changes in the throttle opening controlled to realize the required ce of FIG. 7 (d), and FIG. 7 (f) is to realize the charging efficiency of FIG. 7 (d). FIG. 7G is a chart showing changes in the engine speed of the engine controlled as shown in FIGS. 7E and 7F. FIG. 7G is a chart showing changes in the amount of advance of the intake VVT to be controlled.
As shown in FIGS. 7E and 7F, the throttle valve 6 and the variable intake valve mechanism 18 are controlled so as to realize the required ce shown in FIG. 7D. As a result, the engine speed shown in FIG. 7 (g) increases at a substantially constant rate of increase while changing in accordance with the change in the accelerator opening. The actual output torque of the engine 10 at this time changes so as to substantially match the target torque shown in FIG. That is, it is possible to suppress a decrease in torque accompanying ignition retard for preventing knocking while preventing deterioration of fuel consumption.

  Next, effects of the engine control apparatus according to the above-described embodiment of the present invention will be described.

  First, the PCM 60 sets a target ce for causing the engine 10 to output a target torque according to the reference ignition timing or the ignition timing corrected to the retard side in order to suppress knocking, and sets the target ce as the engine ce. The limit ce set according to the operating state of 10 is limited so as not to exceed, and the intake air amount is controlled according to the request ce limited below the limit ce. Therefore, ce is excessively increased and the thermal efficiency is lowered. By doing so, it is possible to prevent the target torque from being obtained despite the increase in the target ce, and to prevent a vicious circle in which the target ce further increases and the fuel consumption deteriorates. As a result, it is possible to suppress a decrease in torque associated with the ignition retard and prevent deterioration of fuel consumption.

  In particular, the PCM 60 limits the target ce so that it does not exceed the limit ce set so that the thermal efficiency is 30% or more in various operating conditions. Therefore, the target ce is increased by excessively increasing ce. The target torque cannot be obtained even if it is applied, and the thermal efficiency can be prevented from decreasing to a region where the target ce further increases and the fuel consumption deteriorates, thereby reducing the torque accompanying the ignition retard for preventing knocking. Can be suppressed, and deterioration of fuel consumption can be reliably prevented.

  Further, since the PCM 60 limits the target ce so as not to exceed the limit ce set so as to increase as the engine load increases at the same engine speed, the target ce is set to the engine speed and the engine load. Accordingly, it is possible to limit the pressure to be equal to or less than the appropriately set limit ce, and thereby it is possible to suppress a decrease in torque associated with ignition retard for preventing knocking and to reliably prevent deterioration of fuel consumption. .

  Further, since the PCM 60 limits the target ce so as not to exceed the limit ce set so as to be constant in a region where the engine load is relatively high, the target ce is appropriately set according to the engine load. Therefore, it is possible to suppress a decrease in torque associated with ignition retard for preventing knocking and to surely prevent deterioration of fuel consumption.

  Further, since the PCM 60 limits the target ce so as not to exceed the limit ce set almost constant regardless of the engine speed at the same engine load, the target ce is set according to the engine speed and the engine load. It is possible to limit the pressure to be equal to or less than a properly set limit ce, and thereby it is possible to suppress a decrease in torque associated with ignition retard for preventing knocking and to reliably prevent deterioration in fuel consumption.

  The PCM 60 is based on the lower thermal efficiency of the reference thermal efficiency preset according to the target torque and the engine speed and the actual thermal efficiency estimated based on the engine speed, the intake air amount and the ignition timing. Since ce is set, the target ce can be set in consideration of the decrease in thermal efficiency due to ignition retard, which can reliably suppress the torque decrease associated with ignition retard to prevent knocking and reduce fuel consumption. Can be prevented.

DESCRIPTION OF SYMBOLS 1 Intake passage 4 Turbocharger 4a Compressor 6 Throttle valve 9 Air bypass valve 10 Engine 13 Fuel injection valve 14 Spark plug 18 Variable intake valve mechanism 25 Exhaust passage 31 WG valve 40 Accelerator opening sensor 53 Vehicle speed sensor 54 Knock sensor 60 PCM
100 engine system

Claims (4)

An engine control device that controls an engine to output a target torque,
Ignition timing setting means for setting a reference ignition timing by the engine ignition device according to an operating state of the engine;
Ignition timing correction means for correcting the reference ignition timing to the retard side in order to suppress knocking;
The target air amount for causing the engine to output the target torque is determined based on the reference thermal efficiency corresponding to the engine operating state under the condition that the ignition timing is set to the reference ignition timing, or the intake air amount and the engine speed. And target air amount setting means for setting the actual heat efficiency estimated based on the ignition retard amount;
Target air amount restriction means for restricting the target air amount so as not to exceed a threshold set so that a reference thermal efficiency according to the operating state of the engine is not less than a predetermined value;
Air amount control means for controlling the intake air amount in accordance with the target air amount restricted below the threshold by the target air amount restriction means,
The threshold value is set to be almost constant regardless of the engine speed at the same engine load in the region where the engine load is relatively low, and the engine speed is set at the same engine load in the region where the engine load is relatively high. Is set to be higher in the region between the high rotation region and the low rotation region than in the relatively high high rotation region and the relatively low low rotation region,
An engine control device.   The engine according to claim 1, wherein the target air amount restriction means restricts the target air amount so as not to exceed the threshold set so as to increase as the engine load increases at the same engine speed. Control device.   The target air amount limiting means limits the target air amount so as not to exceed the threshold value set so as to be constant in a region where the engine load is relatively high at the same engine speed. The engine control apparatus described in 1. The target air amount setting means sets the target air amount based on the lower reference thermal efficiency or the actual thermal efficiency of the reference thermal efficiency and the actual thermal efficiency. The engine control apparatus described in 1.

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